JPS628488A - Sheathed heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves filling magnesia powder around a heating coil inserted into a metal pipe, and then reducing the diameter of the coil to increase the packing density of the magnesia powder. It is related to the Tanabata Festival.

[Conventional technology]

In the conventional sheathed heater, as shown in FIGS. 4 and 5, a heating coil 2 with lead terminals 3 and 4 connected to both ends is inserted into a metal pipe 1, and magnesia powder 5 is filled into the pipe 1. After that, the opening at the end of the pipe 1 is closed with a temporary 6.7, and as shown in FIG. It is produced by reducing the diameter of the pipe 1 with rollers 8 towards the end.

In such a diameter reduction process, the diameter of the connection parts A and B between the heating coil 2 and the extraction terminals 3 and 4 is reduced, for example, in the A part, the diameter is reduced from the extraction terminal 3 side to the heating coil 2 side,
In part B, the diameter is reduced from the heating coil 2 side to the extraction terminal 4 side.

In the conventional product which is subjected to diameter reduction processing as described above, the diameter of part A in particular is reduced from the extraction terminal 3 side to the heating coil 2 side, so when the diameter of extraction terminal 3 is reduced, the magnesia of The powder 2 has a very high density because the diameter of the extraction terminal 3 cannot be easily reduced.

For this reason, when the density exceeds a certain level, magnesia powder 5
The magnesia powder 5 sequentially moves in the direction of diameter reduction processing. Due to the movement of this magnesia powder 5, the extraction terminal 3
The magnesia powder 5 in the heating coil 2 part of the connection part A with the heating coil 2 increases, and the density of the magnesia powder 5 in this part becomes extremely high due to the diameter reduction process, and the heating coil 2
is greatly compressed. This causes problems such as the heating coil 2 buckling, becoming wrinkled or sheared. This phenomenon becomes more pronounced when the extraction terminal 3 is thicker and the ratio D/d between the outer diameter of the heating coil 2 and the outer diameter of the heating coil 2 becomes larger.

A device in which the heating coil 2 is buckled as shown in Part (B) has the disadvantage of an extremely short service life.

On the other hand, the connection part B between the heating coil 2 and the extraction terminal 4 is
Since the layer of magnesia powder 5 is thicker than that of the portion, and the amount of diameter reduction is constant, there is almost no movement of the magnesia powder 5, and the density does not become higher than that of the extraction terminal 34 portion.

Also, even if there is some movement of the magnesia powder 5, the heating coil 2
This can be achieved by increasing the coil pitch P of
At the connection part B, no problem occurs with the heating coil 2.

[Problem that the invention seeks to solve]

With conventional products, the diameter reduction process is performed from one direction as described above, so the heating coil, especially at the starting end of the diameter reduction where the diameter is reduced from the extraction terminal side to the heating coil side, buckles and becomes wrinkled. In some cases, the wires would be sheared and disconnected. In addition, when the wrinkles form, it is a sudden bending phenomenon, which has the disadvantage of being weak in terms of strength and, of course, having a short lifespan, resulting in the production of unreliable sheathed heaters. Ta.

The present invention has been made to solve the above-mentioned problems, and it prevents shrinkage due to compression of the heating coil at the starting end of diameter reduction, prevents buckling, and provides a long-life and highly reliable seeds. The purpose is to obtain a heater l.

[Means for solving problems]

In the sheathed heater 1 according to the invention of B, the diameter is reduced by inserting a ceramic member having an outer diameter slightly smaller than the inner diameter of the heating coil into the heating coil at the starting end of the diameter reduction.

[Effect]

In the sheathed heater l in the invention of B, the ceramic member inserted inside the heating coil at the starting end of diameter reduction generates heat by moving the magnesia powder and positioning it inside the heating coil when the heating coil is compressed when the diameter is reduced. Prevents coil shrinkage.

[Embodiments of the invention]

1 and 2 show an embodiment of the present invention, in which 1 is a metal pipe, 2 is a heating coil, and 3.4 is an extraction terminal, which is connected to both ends of the heating coil 2, and one It has a protrusion 3a at the end of the extraction terminal 3.

5 is magnesia powder, which is filled in the pipe 1.

6 and 7 are temporary frames that close the end opening of the pipe 1. Reference numeral 9 denotes a ceramic member whose outer diameter is slightly smaller than the inner diameter of the heating coil 2, and a projection 3a provided on one end of the extraction terminal 3.
It has an engagement hole 9a that engages with, and is inserted into the heating coil 2 on the diameter reduction starting end side.

As shown in FIG. 2, the pipe 1 made as described above is reduced in diameter by rollers 8 and the magnesia powder 5 inside is compressed to increase the filling rate and improve heat conduction. At this time, the diameter reduction process is completed by inserting into the roller 8 from the end on the takeout terminal 3 side toward the other end.

In the above embodiment, the ceramic member 9 is inserted into the heating coil 2, so the diameter is reduced by the roller 8 from the extraction terminal 3 side, and the magnesia powder 5 in the portion of the extraction terminal 3 is gradually removed. When it is sent out to the heating coil 2 side and reaches the heating coil 2, the heating coil 2 is compressed and tries to shrink, but it cannot shrink because there is a ceramic member inside the heating coil 2. .

Therefore, the heating coil does not buckle and become wrinkled or break as in the conventional case. Therefore, it can be used with confidence in terms of service life, and reliability is improved.

Note that, as shown in FIG. 3, if the ceramic member 9 is made into a so-called tapered shape, which is tapered toward the tip, there will be no sudden change portion, and the effect will be even greater.

Due to the invention of O, the so-called D/d in Fig. 4 has a small diameter heating coil and a large outer diameter of the coil, which was previously considered difficult to manufacture.
It becomes possible to manufacture products with a large ratio of

〔Effect of the invention〕

As described above, according to the present invention, the diameter of the pipe is reduced by inserting a ceramic member having an outer diameter slightly smaller than the inner diameter of the heating coil inside the heating coil on the side where diameter reduction starts. At the connection between the lead-out terminal on the starting end and the heating coil, the shrinkage of the heating coil due to excessive compression due to the movement of magnesia powder is reduced, which prevents buckling and the occurrence of wrinkles and shearing. It is possible to obtain a sheathed heater l that has a long life and high reliability.

[Brief explanation of the drawing]

Figures 1 to 3 show the sheathed heater l of the present invention, where Figure 1 is a sectional view after filling with magnesia powder, and Figure 2
Figure 3 is a sectional view of the main part after filling magnesia powder, which shows another embodiment, and Figures 4 and 5 show the conventional sheathed heater I. FIG. 4 is a sectional view showing the state after filling magnesia powder, and FIG. 5 is a front view showing the diameter reduction process. In the figure, 1 is a pipe, 2 is a heating coil, 3 and 4 are extraction terminals, 5 is magnesia powder, and S is a ceramic member. Agent: Masuo Oiwa (2 others) 9=Zefmic 4ψSuga 2 figures 3 figures 4 figures 5 meters

Claims (2)

[Claims] (1) A heating coil with extraction terminals connected to both ends is inserted into a metal pipe, the pipe is filled with magnesia powder, and then the diameter of the pipe is reduced from one end to the other. A sheathed heater characterized in that the diameter is reduced by inserting a ceramic member having an outer diameter slightly smaller than the inner diameter of the heating coil into the heating coil at the starting end of the diameter reduction. (2) The sheathed heater according to claim (1), wherein the ceramic member has a tapered shape that becomes thinner toward the tip.